Abrading machine and method of grinding



May 2, 1933. w WUERFEL 1,906,731

' ABRADING MACHINE AND METHOD OF GRINDING Filed Sept. 23. 1926 4Sheets-Sheet l liNVENTOR: HW/I'am 170627524 ATTORNS.

My 2, 1933; w. WUERFEL ABRADING MACHIN E AND METHOD OF GRINDING v FiledSept. 25 1926 4 Sheets-Sheet 2 Milt! Q m \M N 42 .1 Q I nab:

- mm Iii/6x124 INVENTOR:

ATTORNEYS.

May 2, 1933. w w EL. 1,906,731

ABRADING' MACHINE AND METHOD OF GRINDING Filed Sept. 25, 1926 4Sheets-Sheet 5 J5? v w 3 INVENTOR: m/fi'am 17216772 4 '5 ATTORNEYS.

May 2, 1933. w. WUERFEL ABRADING MACHINE AND METHOD OF GRINDING FiledSept. 25, 1926 4 Sheets-Sheet 4 Patented May 2, 1933 PATENT OFFICEWILLIAM WUERIFEL, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO WILKENINGMANUFACTURINGCOMPANY, OI PHILADELPHIA, PENNSYLVANIA, A CORPORA- TION OFDELAWARE ABRADING MACHINE AND METHOD OF GRINDING Application filedSeptember 28, 1926. Serial No. 137,240.

My invention relates to a new and useful grinding or abrading machine,adapted to grind two opposed flat surfaces, to smoothly finishedparallel planes, by means of suitable abrasives. My machine ispartlcularly adapted for grinding opposed fiat surfaces of discs, ringsor the like, to smooth highly finished and perfectly parallel planes; asfor 1 nstance, the opposed flat faces or edges of plston rings. I

In grinding the opposed parallel surfaces of piston rings, it has beenthe practice heretofore, to place the piston rings individually, betweenthe juxtaposed flat and parallel revolving abrasive surfaces and toretain the individual piston rings fixedly between such flat and.parallel abrasive surfaces, until ground down to the desired thicknessand finish. In these prior art machlnes, the abrasive surfaces wereformed on two disc-shaped grind stones carried by suitable spindles andjuxtaposed to each other at a suitable dlstance. To insert the ringinitially, between thesetwo juxtaposed grinding surfaces, it wasnecessary, and hence it was the practice, to separate the two grindstones a greater distance, position the ring, by means of a suitablering holder, between the twogrmdlng surfaces, and then move the grindingstones towards each other, into engagement with the opposed edges of thepiston ring. The revolving grind stones were then pressed towards eachother, until the ring was ground down to the desired thickness.Thereafter, the grind stones were again separated and the finished ringremoved from between the same.

' By the prior art practice it was therefore necessary and essential toseparate the two grinding surfaces and then to bring them to-- alsorequired a manual operation for the insertion and removal of theseindividual piston rings, as well as a manual feeding of the grind stonesto the finished dimensions. By

the machine and construction of my present invention, I am enabled tofeed a. continuous series of piston rings through and between twouxtaposed revolving grinding surfaces, without changing the distancebetween the two grinding surfaces, for the insertion and removal of thepiston rings, or for the actual removal of the metal to the finishedthickness of the ring. i

In order to overcome and eliminate these disadvantages andinsufiiciencies of the prior art practice, my invention contemplates anovel grinding machine, having two. opposed grinding discs or wheels,having juxtaposed circular grinding surfaces which are substantiallycontinuous and preferably without any indentations or aperturestherethrough, said grinding surfaces being placed at a slight angle toeach other, at a suitable distance apart, so that the surfaces willdiverge toward one point along the periphery thereof, so that theunfinished or rough piston ring may be freely inserted at that point,without separating the grinding'wheels further to permit the insertionof the rings.

Thus I may either provide two grinding or abrasive discs having slightlytapered or conical opposed surfaces, placed upon the juxtaposed ends oftwo axially aligned spindles whereby the opposed surfaces of saidgrinding wheels will converge slightly from the periphery thereoftowards the center of rotation, so. that the piston ring may initiallybe inserted between the two grinding discs at the diverged outerperipheral edge, and fed gradually towards the center, either by gravityor otherwise, as it is being reduced in thickness, by the abrasiveaction of the two opposed revolving grinding discs.

In lieu of the slightly tapered or conical discs, however, I may providetwo grinding discs having perfectly plane opposed surfaces, in whichcase the shafts or spindles carrying the two discs are deflected orinclined slightly out of axial alignment with each other, so as todiverge the two opposed grinding surfaces slightly across a diameter ofsaid discs. In this embodiment of my invention, the grinding surfaceswill converge from one point along the periphery,

straight across the grinding surfaces, to a diametrically opposedperipheral point and the piston ring will then be inserted at thepointof greatest divergence and will be fed between the grindingsurfaces in a diametrical direction to the opposed point of greatestconvergence, at which oint they will be abraded to the desired Inanother embodiment of my invention however, I may provide both aninclined spindle as well as a conical or tapered grinding wheel. By thislatter embodiment of my invention, two juxtaposed, slightly conical ortapered rotating abrasive discs are mounted upon two spindles slightlyinclined or slightly deflected from axial alignment with each other, sothat in the plane of the deflection of the spindles, it is possible toincline the grinding surfaces with respect to each other on one side ofthe center of rotation, and maintain said grinding surfaces more or lessparallel to each other in a diametricall opposed direction, on theopposed side of 1 t e center of rotation. Thus, in this embodi wards thecenter of rotation of the abrasive discs, in a diametrical or radialdirection, as

they are being reduced in thickness by the abrasive action. While sobeing ground down or reduced in thickness, the opposed edges of thepiston rings may be slightly out outwar y in a radial direction throuhout their circumference, to the extent of t e inclination ofthe twoabrasive surfaces. How-' ever slight this ta r may be, it is entirelyeliminated as the piston rings pass the center.

i v of rotation of the grinding discs and pass between the two more orless parallel portions of the opposed grinding surfaces, that is, theportion on the other side of the center. In passing through theparallel'portion of the grinding wheels, also in a radial or diametricaldirection, they are ground down perfectly parallel, and plane, to thedesired thickness, which is determined by the dis; tance between themore or less parallel zone-- of the wheels. The piston rings then emergeat an-opposed peripheral point, in perfectly. parallel and finishedcondition. One of the objects of my invention. is

obtain great accuracy and uniiormityin parallel surfaces of machineelements, as for instance, piston rings, wrist pins, and the like, bycausing the end-pointof the. final' grinding, and hencethe finalfinished dimension of the ground surface, to be determined by the final'gravitational discharge of the nished thickness.

' allel there I -rings to ,-triie parallel p anes. In the preanewmachine element frombetween two abrasive surfaces.

With the above ends in view, my invention consists of a suitable.housing or frame, two pairs of juxtaposed journals mounted upon saidhousing and adapted for an axial movement for varying the distancebetween the grinding wheels or discs, and also adapted for two angulardeflecting movements in two different planes at a right angle to g eachother, whereby the two opposed pairs of journals may be deflected withrespect to each other in two different planes, from their normal andaxially aligned positions, so as to placethe two axes of the journals atany desired inclination to each other.

My invention further consists of a suitable pair of opposed spindlesrotatably carried by the opposed pairs of journals, and suitableabrasive discs or wheels carried by the juxtaposed or inner ends of saidspindles, and suitable means for revolving said spindles, such aspulleys, ears or the like.-

LIy invention urther consists of a pair of opposed abrasive discs orwheels carried by the inner or juxtaposed ends of said spindles, havingtwo slightly conical or tapered 'uxtaposed abrasive surfaces, wherebysaid a rasive surfaces will diverge from the center outwardly, towardsthe peripheries, to a sulficient extent so that the unfinished ring maybe inserted at the periphery. Such divergence or inclination may befurther varied by the deflection-of the axis of rotation ofsaid'spindles, by the means mentioned hereinbefore.

Bfy positioning the two juxtaposed grinding of true (parallel, that is,they will be tapered .sur a at the peripheral point of greatestivergence,

and then to pass 'thelring in a diametrical direction towards thecenters of the discs, thereby reducing the thickness thereof, andfinally passing the ring outwardly towards the peripheryybetween themore or less pary finishing" the op osed edges of the ferred 'ractice'ofmy invention, the rings are ed to gravitate downwardly through thewo-reyolving abrasive surfaces, by their own weight,funtil they areground down to. the desired'finished thickness in between the lower andmore or less parallel portions of the grinding surfaces. In thepreferred practice of my invention, moreover, the inding discsare'revolved in opposite directions.

For the purpose of illustrating my invenportions of the revolvingabrasive discs,

tion, I have shown, in the accompanying drawings, formsthereof which areat present preferred by me, since they will give in practice,satisfactory and reliable results, although it is to be understood thatthe various instrumentalities of which my invention consists can bevariously arranged and organized and that my invention is not limited tothe precise arrangement and organization of these instru-. mentalitiesas herein shown-and described.

Referring to the drawings,

Figure 1 represents a front elevation of a machine embodying myinvention, illustrated in a diagrammatic manner.

Figure 2 represents a top planview of the same. I

Figure 3 represents a section on line 33 of Figure 2, on a greatlyenlarged scale.

Figures 4, 5, 6 and 7 represent diagrammatic illustrations of thealternative manners of inclining the two grinding discs with respect toeach other.

Figure 8 represents a section on line 8-8 of Figure 3.

Figure 9 represents a section on line 9-9 of Figure 3.

Figure 1.0 represents a novel arrangement of a series of machines of mynovel construction, whereby the piston rings may be ground to successivedimensions and degrees of finish, through a series of successivelygraded machines, instead of by a single machine.

Figure 11 represents a similar arrangement or series of machines,whereby the piston rings may gravitate through the successive machines,without any mechanical conveying means.

Referring to the drawings, in which like reference characters indicatelike parts, 1 desi nates a frame or housing of my novel ma- 0 i e,having two opposed horizontal and subs antially similar upper circularbeds 2 and 3, each having a corresponding central pivot socket 4 and 5respectively, adapted to receive the corresponding pivot pins 6 and 7respectively, of the corresponding turn-tables 8 and 9 respectively.Each of the two opposed turn-tables 8 and 9, is provided with suitablearcuate slots 10, centered about the corresponding lpivot pins 6 and 7.The bolts 11 pass throng the arcuate slots 10 and are threaded intocircular beds 2 and 3 respec-' tively, thereby rigidly to secure therotatable turn-tables Sand 9, in any desired adjusted position, that is,in any angularly inclined position with respect to each other.

Each of the turn-tables 8 and 9 is provided with a correspondingconcaved arcuate tilting bed or surface 13 and 14 respectively, uponwhich are mounted the corresponding tilting heads 15 and 16respectively, having corresponding convexed lower surfaces, seated uponsaid concaved beds. Suitable arcuate guide slots 17 and 18 respectively,are provided in the two corresponding tilting beds 13 and 14, into whichcorresponding arcuate guide ribs 19 and 20 project, thereby to guide thetilting heads 15 and 16 upon the beds 13 and 14 respectively. Each ofthe tilting heads is also provided with the slots 21, through which thebolts 22 pass, which in turn are threaded into the tilting beds, therebyrigidly and fixedly to secure the two tilting 28, and 29 and 30respectively. Each of the V spindles3l and 32 carries a suitable pulley33 and 34 respectively, adapted to receive a suitable belt or the like,(from countershafts not shown in the drawings, whereby the spindles.

may be suitably revolved, preferably in opposite directions, and thejuxtaposed ends of the spindles carry corresponding opposed circular,grindingdisc supports or holders 35 and 36 respectively. Each of thegrinding disc supports or holders 35 and 36, comprises a circular discshaped portion positioned at a right angle to the axes of the spindles,and centered with respect thereto, having the laterally and oppositelyprojecting peripheral flanges 37 and 38 respectively. I

Grinding or abrasive discs 39 and 40 are secured to the holders orsupports 35 and 36, ina manner shown particularly in Figure 3. Thus'thegrinding discs 39 and 40 are provided with annular V shaped flanges 41and 42 at the rear surface thereof, and extending around the entireperiphery. Split V shaped locking rings or retaining rings 43 and 44 areplaced about and inlocking engagement with, the flanges 41 and 42, andare in turn engaged by a series of screws 45, and extending through theplates 35 and 36 and threaded into said split rings 43 and 44,respectively. By this means, the grinding or abrasive wheels or discs 39and 40 are brought up tightly against the flat inner surfaces of thesupports or holders, and retained there rigid ly. By this means, theabrasive discs are secured to the spindle ends, without the latterextending through the center of said grinding discs, thereby leaving theopposed surfaces of the abrasivediscs entirely clear and free of anyprojection, or retaining means.

Each of the journal blocks 25 and 26 is provided with a downwardlyprojecting lug 46 and 47 respectively, having longitudinal threadedopenings extending therethrough for the reception of the feed screws 48and 49 respectively, which in turn are journalled in correspondingbearing openings 50 and 51 respectively, and to the outer ends thereof,corresponding hand wheels or handles 52 and 5 53 respectively; aresecured. By this means, .the journal blocks 25 and 26 may be movedlongitudinally towards and away from each other, by merely revolving thehandles 52 and 53 respectively, thereby to vary the distance between thegrinding surfaces of the abrasive discs 39 and 40, as may be desired forregulating the finished thickness of the piston rings.

It will thus be seen from the foregoing that by the novel provision ofthe turn tables 8 and 9, and the tilting heads 15 and 16 mountedthereon, it is possible to deflect or incline the two spindles 31 and 32at, any desired angle with respect to each other, (within the limits ofthe machine), thereby to incline the opposed faces of the grinding discsat any desired angle with respect to each other. Thus by tilting theheads 15 and 16, the shaft or spindle 31 and 32 are deflected in avertical plane, while by revolving the turn tables 8 and 9 respectively,the spindles 31 and 32 are deflected in a horizontal plane. When iproperly deflected the spindles may be fixed in the angularly adjustedpositions, by the bolts 11 and 22 respectively, as pointed outhereinbefore. Bythe combination of the two angular adjustments, to wit,the vertical inclination and the horizontal inclination, the twospindles may be deflected in any plane Intermediate the vertical andhorizontal, and to any degree within'the limits of the machine, as maybe desired. 1' I In Figures 1, 2 and 3, there are shown the preferredtype of grinding discs or wheels, havlng the opposed surfaces thereof ofa slightly conical shape, indicated diagrammatically in Figures 5 and 7.Thus, the opposed surfaces 55 and 56 are each tapered outwardly from thecenter or axis of the discs, to a suitable degree, so that the two discswhen placed upon aligned axes, will diverge from the centers towards theperipheries of the two opposed grinding surfaces, whereby it is possible to insert the piston rings to be ground, without separating thegrinding surfaces for the operation of insertion, but merely insertingthem at the periphery where they are more distant, and then allowing thepiston rings to be fed or moved towards the center of rotation, of theconverging surfaces,'as the thickness of the rings is being reduced bthe abrasive action of the two grinding su aces. The amount of tapernecessary between the two opposed grinding surfaces depends primarily onthe amount of metal necessary to be removed from the opposed edgesurfaces of the piston ring, and upon the diameter of the grinding discsor wheels. It will thus be i seen that with abrasive discs or wheels ofapproximately inch diameters, and with the amount of metal to be removedapproximately ten to fifteen thousandth of an inch, more or less, theamount of inclination used will be but very slight, to wit, possiblyfifteen to twenty thousandth of an inch between the outer periphery atthe point where the piston rings are inserted between the abrasivediscs, and the pointswhere thediscs approach each other the closest, towit, where the distance is substantially equal to the thickness of thefinished ring. I

Considering first the embodiment of my invention, that is, themodification shown in Figures 1, 2 and 3, and Figures 5 and 7, there areshown grinding discs or abrasive wheels, having slightly tapered orconical grinding surfaces and 56 respectively. In employing thismodification it is possible so to adjust the inclination of the twospindles 31 and32, as tobring the maximum inclination between theabrasive surfaces, entirely on one side of the abrasive discs. Thus,with the spindle 32 in the neutral and horizontal position, shown inFigure 5, the spindle 31 may be tilted or deflected from its normalposition,

until the lower portions of the conical discs are entirely parallel toeach other. It is preferred however, to tilt or deflect both thespindles 31 and 32, each to half the extent, as indicated in the diagramin Figure 7. In this manner, it will thus be seen, that while the upperhalves of the two opposed grinding surfaces in the plane of deflectionof the spindles, diverge towards the. periphery, the lower portionsthereof, in the same plane, are entirely and perfectly parallel. Thus byinserting the piston ring at the upper or diverged peripheral edges ofthe abrasive discs, they will be ground down to the desired thicknes,

while moved from theouter'periphery towards the center of-the revolvinggrinding discs, and will be'finished to the exact desired thickness andwill be finished moreover perfectly parallel as they pass through andbetween the lower more or less parallel halves of the two revolvinggrinding discs.

Since the amount of divergence. of the grinding surfaces is slight,relative to the diameters of the opposed abrasive surfaces,

it.is quite feasible and possible to produce substantially parallelopposed edge surfaces on the piston rings, by two inclined or slightlydiverged grinding surfaces as shown in Figures 4 or 6. In thismodification the surfaces of the grinding discs are not tapered orconical, but are perfectly plane, and the amount of divergence necessaryat the point of insertion of the rings is obtained entirely by theinclination of the grinding surfaces. by the tilting of the axes, of thespindles 31 and 32. Thus, in Figure 4 there is shown an arrangementwherebyrne of the axes 31 is alone tilted or deflected while in Figure 8both axes are tilted or deflected, to one half of the extent however, inorder to obtain the necessary divergence at the upper, or pointofinsertion of the ring.

It will be observed that by passing the ring through and between the twoopposed grinding surfaces of the revolving abrasive discs 39 and 40,there is a tendency for the piston rings to revolve constantly, due tothe slight differences in the force exerted upon the edges of the ringby the two grinding surfaces. This revolving action on the piston ringsis also accentuated and increased by feeding or passing the piston ringsin a line slightly off a true diametrical direction, that is, slightlyoff the center of the abrasive discs. It is partly due to this constantrotation of the piston rings, as they pass through and between the twojuxtaposed revolving abrasive surfaces, that the rings are grounduniformly throughout their entire circumferences.

Referring to Figures 1, 2 and 3, and 9, there is shown a novelarrangement whereby the piston rings may be fed through and between thetwo opposed grinding surfaces 55 and 56 of the grinding wheels 39 and40. Thus a series of aligned piston rings 58 are positioned in asubstantially horizontal stack in a horizontal, or substantiallyhorizontal trough or guide channel 59. One end of the trough is insubstantial vertical alignment with the grinding surfaces of theabrasive wheels and has secured thereto, a transverse guide 60, having abottom 61 and two parallel side plates 62, spaced from each other at adistance substantially equal to the thickness of the unfinished ring, sothat but a single ring can passbetween the plates 62. A pair of suitablefeeding arms 63, supported upon a shaft 64, are provided for the purposeof forcing the individual rings from the stack 58 into the transverseguide-60. A handle 65 is provided on the shaft 64 for the purpose ofrevolving said shaft and thereby to feed the individual rings into thetransverse guide 60.

The side plates 62 of the transverse guide 60, are continued downwardlyin the supporting plates 66, to which are adjustably secured the upperterminals of a pair of guide strips 67, of a thickness somewhat lessthan.

that of the finished piston rings, so that they will clear the abrasivediscs, when placed between the two grinding surfaces 55 and 56, withoutbeing affected by said grinding surfaces. The distance between the twoguiding strips is adjusted or controlled by any suitable. means, such asthe series of openings 68 in the plates 66. The guide-strips 67 may thusbe secured rigidly in any desired adjusted position to suit the diameterof the particular size ring, by means of the two screws or the like 69,passing through the two plates 66, as indicated particularly-in Figures1, '2,

3 and 9. The lower terminalsof the guidestrip 67 are similarly securedto a lower trans verse supporting member 70, which is rigidly secured tothe frame, so that the two guidestrips may be maintained rigidly andparallel to each other against the dislodging force of the grindingsurfaces upon the ring, tending to carry the rings out of the linearpath between the two parallel guide strips 67. By means of the gui estrips 67, the piston rings are fed through and between the two grindingsurfaces 55 and 56 in a'straight path from the upper peripheral point ofinsertion to the lower peripheral point of discharge of the rings,substantially diametrically opposed to it, and the rings are preferablypassed in a generally downward direction, so that the piston rings willbe urged toward the peripheral discharge point of the grinding wheels,by gravity.

In Figure 9, the guiding strips 67 are shown arranged substantiallysymmetrically with respect to the axis of the spindles although theguiding strip may be offset a slight distance from the symmetricalarrangement shown. By offsetting the guide strips 67 an additionalrotarymotion is imparted to the piston rings, as they travel downwardlybetween the two revolving grinding surfaces, thereby producing a moreuniform and finer finish throughout the circumference of the edges ofsaid rings.

It will thus be seen, that by my novel construction it is possible topass a series of piston rings through and between a pair of opposedrotating grinding surfaces, in a continuous and uninterrupted manner,without changing the distance between the grinding surfaces for theinsertion and removal of the piston rings. This, as brought outhereinbefore, is made possible by the slight divergence of the twogrinding surfaces towards the point of insertion of the ring. Thus, inany one of the several modified arrangements indicated diagrammaticallyin Figures 4 to 7 inclusive the farthermost point of the two grindingsurfaces is at the point of insertion of the ring. By the provisioniofthe slightly conical or tapered grinding wheels it is'p'ossible moreoverto have the grinding surfaces perfectly parallel at the bottom, whilethe top halves of the wheels diverge, as shown in Figures 5 and 7.

The degree of inclination between the two grinding surfaces may, in anyinstance, be reduced somewhat by suitably beveling theopposed peripheralcorners of the grinding discs or wheels, so as to facilitate receptionand grinding of machine elements which may be of slightly greaterinitial dimension.

Since by my novel construction, the indi-' vidual manual insertion andremoval of the rings is thus entirely eliminated, I am enabled tocoordinate a plurality of gginding a series arrangement, to wit, I amenabled to pass a continuous series of piston rings through successiveand aligne machines, each adapted to remove successive amounts of metaland thus to reduce the rings to successive thicknesses.

Thus, the maximum amount of metal should be removed in the first orsecond machine, allowing the last machine to remove but a very slightamount of metal, thereby producing a more accurate and more finelyfinished ring.

Two arrangements of this type, are shown in Figures 10 and 11respectively. Thus, in each of these figures there are shown threemachines, designated by the numerals 72, 73 and 7 4, illustrated merelyin a' diagrammatic manner, without reference to the detail constructionthereof. In the modification shown in Figure 10, there is arranged ontop of the machine 72, the feeding device 75 of substantially the samenature as that shown in Figures 1 to 3 inclusive; together with theguide strips 67. The rings 58 are fed into the guide strip 67 in theusual manner and gravitated through the abrasive wheels of the firstmachine. Here the are guided by another suitable lower gui e 76 onto asuitable continuous bucket conveyer 77 of any desired construction,which raises the individual rings and places them onto a second guide78. From there, the piston rings again gravitate down through andbetween the two revolving abrasive discs of the second machine, guidedby the guide strips67. A similar guide 7 9 guides the rings onto asecond conveyor 80, which delivers the rings onto the guide 81 at thetop of the last or finishing wheels of the machine 74.

In the arrangement illustrated in Fi re 11, thesuccessive sets ofrevolving grin ing discs 81, 82, and 83 as well as their respectivemountings and spindles etc. are positioned-at successive levels, so thattheir successive centers of rotation or axes of rotation, will bepositioned in substantial alignment with each other along an inclinedline, as will readily be seen from Figure 11. B this arran ment it ispossible to'provi e substantia ly continuous guiding means, such as theguide strips 84 and 85, and the side guide plate 86, arranged in asubstantially continuous manner, through wheels, so that t without theintervention. of any mechanical feeding or conveying devices. 4

It is to be understood that in the drawings accompanying this descrition there have been illustrated merely so ematic showings of theembodiment of my invention and chiefly in adiagrammatic manner, and themachine is, therefore, not limited to the exact arrangement "of elementsas shown in-these figures.

th S c es ive d n e 'p e tr ng .8 my a tate'through the successivegrinding-wheels "in a continuous and uninterrupted, manner 'tivelyinclined and oppositely revolving abra- Thus for instance, in the twoarrangements of successive sets of grinding wheels shown in Figures 10and 11', it is quite feasible and practicable, and possibly more 5desirable to build the successive sets of grinding wheels upon a singleframe, that is, to build them into one machine, rather than intosuccessive independent machines as shown in the drawings. This, it isunderstood, will not in any way de art from the spirit of the inventiondisclose in these figures.

Thus, also, in Figures 1, 2, 3, 8 and 9, the means shown for adjustingthe distance between the grinding wheels or abrasive surfaces, that is,the slide and the screw feed therefor have been merely illustrated in asomewhat diagrammatic and conventional manner, it being understood thatin the finished embodiment of this invention, such means may be alteredto suit practical requirements without departing from the spirit of theinvention. Similarly, diagrammatic means have been merely shown forobtaining the two angular adjustments of the axes of the spindles.

It will thus be seen, that gravitating the machine elements to beground, through and between two abrasive surfaces more or less inclinedwith respect to each other, with frictional contact being maintainedbetween the machine element and the op osed abrasive surfaces againstthe force 0? grinding end-point or the limit of grinding is determined,and the finished dimension of the work is likewise determined by thegravitational force on the work or machine element overcoming the.frictional grip of the grinding surfaces on said work or machineelement. This determination of the grinding end-point, and hence offinished dimension, b the gravitational discharge of the wor against thefrictional grip of the abrasive sur-,

esir

faces is particularly able in the final or finish-grinding of machineelements which iny. invention to be considered in all respects asillustrative rather than restrictive ;ref-

erence being bad to the appended claims rather than the foregoingdescription to indicate the scope of the invention.- Having, thusdescribed my invention, what I claim as newand desire to secure byLetters' Patent is: I r

1. The method of finishing opposed lane parallel surfaces of machineelemnts, such as piston rings or the like,whichconsists in -maintainingsuch elements between and in abrasive contact with two opposed,operasive surfaces extending transversely of their axes of rotation,while gravitating said ele ments from one peripheral point of saidabrasive surfaces to another, in the general direction of theconvergence of said surfaces.

2. The method of finishing opposed plane parallel surfaces of machineelements, such as piston rings or the like, which consists insuccessively maintaining such elements between and in abrasive contactwith successive sets of two opposed, operatively inclined and oppositelyrevolving abrasive surfaces extending transversely of their axes ofrotation, while gravitating said elements from one peripheral point ofsaid abrasive surfaces to another, in the general direction of theconvergence of said surfaces; said successive sets of opposed inclinedabrasive surfaces being spaced successively closer.

3. A grinding machine including, in combination, a pair of revolublymounted abrasive members, each having a relatively imperforate effectivesurface extending transversely of its axis of rotation, said pair ofeffective surfaces being in juxtaposition and operative-1y inclined toeach other in a generally radial direction and to a suitable degree,with the most distantly spaced peripheral points of said effectivesurfaces positioned higher than the most closely spaced peripheralpoints thereof, and a pair of generally parallel spaced, stationaryguides disposed between said abrasive members to form a fixed passagewaytherebetween for the objects to be ground, with the receiving end ofsaid passageway positioned higher than the discharge end thereof, toguide said objects in abrasive contact with said juxtaposed andgradually converging effective surfaces. I

4. A grinding machine comprising a pair of revolubly mounted abrasivemembers, having a pair of juxtaposed efiective surfaces in spacedrelation to each other, extending transversely of their axes ofrotation, said pair of effective surfaces 'being operatively inclinedwith respect to each other, and means for maintaining the objects to beground, between and in abrasive contact with said pair of operativelyinclined effective surfaces and conveying them by gravity in the generaldirection of their convergence, from one peripheral point of saideffective surfaces to an-' other.

5. A grinding machine including, in combination, a pair of revolublymounted abrasive members, each having a relatively imperforate effectivesurface extending transversely of its axis of rotation, said pair ofeffective surfaces being in juxtaposition and opera: tively inclined toeach other in a generally radial direction and to a suitable degree,with the most distantly spaced peripheral points of said effectivesurfaces positioned higher than the most closely spaced peripheralpoints thereof, a pair of generally parallel spaced, stationary guidesdisposed between said abrasive members to form a fixed passagewaytherebetween for the objects to be ground,,with the receiving end ofsaid passageway positioned higher than the discharge end thereof, toguide said objects in abrasive contact with said juxtaposed andgradually converging efl'ective surfaces, and means for revolving saidabrasive members in opposite directions.

6. The method of finishing opposed surfaces of machine elements, whichconsists in maintaining such machine elements between and in abrasivecontact with two inclined and oppositely revolving abrasive surfacesextending transversely of their axes of rotation and generallyconstantly spaced from each other, while gravitating said elements fromone peripheral point of said abrasive surfaces to another peripheralpointthereof, generally in line with the inclination of said surfaces,and causing said elements to be discharged when the gravitational forceon the same overcomes the frictional grip of the abrasive surfaces uponthe same, and determining the end-point of the grinding operation bysuch gravitational discharge.

7. The method of finishing opposed surfaces of machine elements, whichconsists in successively maintaining such elements between and inabrasive contact with successive sets of two inclinedand oppositelyrevolving abrasive surfaces extending transversely of their axes ofrotation and being generally constantly spaced from each other, whilegravitating said elements from one peripheral point of said abrasivesurfaces to another peripheral point thereof, generally in line with theinclination of said surfaces, and

causing said elements to be discharged from between two inclined andoppositely revolving abrasive surfaces, when the gravitational force onthe same overcomes the frictional grip of the abrasive surfaces upon thesame, and determining the end-point of the grinding operation, and hencethe ground dimension, of the finished machine element by suchgravitational discharge; the effective distance between the two abrasivesurfaces of the successive sets being successively less.

8. A grinding machine including, in combination, a pair of revolublymounted abrasive members, each having a relatively imperforate effectivesurface extending generally transversely of its axis of rotation, saidpair of effective surfaces being in juxtaposition and being inclined toeach other in a generally radial direction, with the direction or lineof inclination being at an angle with respect to-the horizontal, meansfor maintaining said effective abrasive surfaces in generally constantspaced relation to each other while the machine is in operation, a pairof generally parallel spaced, stationary guides disposed between saidabrasive members to form a fixed passageway therebetween for the objectsto be ground, said pair of generally parallel, spaced stationary guidesbeing arranged generally in' line with the direction or line ofinclination of said abrasive members and at an angle with respect to'the horizontal with the receiving end of said passageway positionedhigher than the discharge end thereof, to guide said objects in abrasivecontact with said juxtaposed and inclined abrasive surfaces, saidgrinding machine being so arranged that the objects to be ground aredischarged from between the two abrasive surfaces by gravity when theobject to be ground has been ground to the desired and predetermineddimension, which is attained when the gravitational force upon theobject overcomes the frictional grip of the abrasive surfaces upon thesame.

9. A grinding machine comprising a pair of revolubly mounted abrasivemembers, having a pair of opposed effective surfaces in predeterminedand generally constant spaced relation to each other, extendingtransversely of their axes of rotation, said pair of efiective surfacesbeing slightly inclined with respect to each other, means formaintaining the objects to be groundbetween and in abrasive contact with;-said pair of inclined surfaces,'-'and"for conveying them by gravity inthe general direction of their inclination from one peripheral point ofsaid effective.

surfaces to another peripheral point thereof, and for causing theautomatic discharge of the ground object from between the opposedabrasive surfaces when the gravitational force upon the object overcomesthe frictional grip of the abrasive surfaces upon the same, and fordetermining the end-point of the grinding operation by said automaticdischarge. f I

10. A grinding machine, including, in combination, apair ofrevolubly-mounted abrasive members, each having a relatively imperforate effective surface extending transversely ofits axis of rotation,said air of efiective surfaces beingopposed an in a. generally constantspaced relationto each other,

and being inclined with respect to each other w in a generally radialdirection and to a suitable degree, withthe direction of inclinationbeing at an anglew the horizontal, a pair of generally parallel, spacedstationary guides disposed between'said abrasive members to form a fixedpassageway therebetween for the I 7 objects to be ground, with thereceiving end of said passageway, positioned higher than Y thedischarge'end thereof, to. guide said ,objects inabrasive contact withsaid opposed I and inclined abrasive surfaces, said grinding machine.being so arranged that the objects to be ground are discharged frombetween the

